Radioactive shaped charges and method for well perforating

Methods and apparatus utilizing a shaped explosive charge assembly in a process for perforating earth formations from a well bore whereby the maximum depth of the mean depth of a perforation penetration may be determined. The charge assembly, shaped to produce a perforating jet on detonation, is provided with a gamma ray emitting substance which is deposited at a specific locus in the path of the perforation. By measuring degradation of the gamma radiation detected by a detector 38 in the well bore as by obtaining a ratio of radiation count rates in a first energy range sensitive to primary radiation with minimal Compton scattering and a second energy range sensitive to radiation degraded through Compton scattering, an indication of the depth of perforation is obtained. In one form of the charge assembly 10 the radioactive substance 20 is affixed in a manner, such as at the apex of a conical liner 17 recessed inwardly of the front of the charge 12, whereby upon charge detonation, the radioactive material is deposited by the perforating jet at the maximum depth of perforation and the measurement of spectral degradation provides an indication of maximum depth of perforation. In a second form of charge assembly 60, the radioactive material 65 is affixed in a manner, such as to uniformly cover the surface of the liner 64 disposed against the explosive charge 61, whereby upon detonation and perforation of the formation, the radioactive material is uniformly distributed along the perforation path and the measurement of spectral degradation provides an indication of mean depth of perforation.